Transistors are commonly utilized in integrated circuits, and may have many applications throughout memory, logic, etc. For instance, transistors may be utilized in dynamic random access memory (DRAM) arrays, NAND flash, etc.
A continuing goal of integrated circuit fabrication is to create higher levels of integration, and accordingly to reduce size and spacing of existing components. It is becoming increasingly difficult to reduce the size of transistors due to short channel effects and other complications.
Transistor performance may be characterized by numerous metrics, including, for example, current flow through the on state (Ion) of the transistor and current flow through the off state (Ioff) of the transistor. It is desired to have high Ion without leakage so that current is controlled and relatively unimpeded when the transistor is in the on state; and it is desired to have low Ioff. Often there may be some level of leakage through transistors, especially as the transistors become increasingly smaller. An example leakage mechanism is hot electron induced punchthrough (HEIP), which can be particularly problematic in transistors having short channels.